1. Field of the Invention
The present invention relates generally to a call admission method in a CDMA mobile communication system, and in particular, to a call admission method considering call characteristics and the service class of a subscriber terminal.
2. Description of the Related Art
Today's rapid growth in the mobile communication industry increases the demand for a mobile communication system that is capable of providing multimedia services including transmission of data and pictures as well as typical voice services. This mobile communication system is called the future mobile communication system. This future mobile communication system generally operates in CDMA (Code Division Multiple Access). The CDMA systems are deployed in a synchronous scheme or in an asynchronous scheme. Europe and Japan employ the asynchronous scheme, whereas the U.S. employs the synchronous scheme. Therefore, different standardization works are under way in the U.S. and Europe. The European future mobile communication system is UMTS (Universal Mobile Telecommunication Systems) or W-CDMA (Wideband Code Division Multiple Access).
A variety of regulations should be defined for multimedia services, besides voice call services, in the on-going standardization work for the future mobile communication system. Among them, an efficient call admission scheme is a major issue.
In general, the CDMA mobile communication system has limited radio resources available for a UTRAN (UMTS Terrestrial Access Network) to assign to UEs (Unit Equipments). To properly assign the limited resources for traffic generated from the UEs, a call admission method should be exploited.
The W-CDMA mobile communication system can afford to provide multimedia services efficiently that support QoS (Quality of Service) for each transport channel. However, it cannot implement a reliable call control for unexpectedly generated traffic. The unexpected traffic includes a frequent handoff and a call setup request for a special use from a UE. Moreover, an efficient, immediate call process cannot be provided when overload is imposed on the UTRAN due to excessive call processing requests.
This situation impedes implementation of fast and reliable services in the W-CDMA mobile communication system. What is worse, the ever-increasing packet data service makes it more difficult to ensure QoS through call admission control and efficient bandwidth management.
Accordingly, there is a pressing need for a call admission control which considers the characteristics of a requested call and the service class of a subscriber terminal. For this purpose, a novel RRC (Radio Resource Control) message and its related operation must be offered.